Cooling jackets enable heat to be extracted from the cylinder head of an internal combustion engine. Two piece water jackets have been designed to increase the amount of heat that can be removed from the cylinder head to improve engine performance.
A cylinder head including a two-piece water jacket is disclosed in U.S. Pat. No. 7,367,294. Two embodiments of a coolant flow path are shown. In a first embodiment the coolant flows through the two water jackets in a series configuration in which coolant is directed from the outlet of the lower cooling jacket to the inlet of the upper cooling jacket. In a second embodiment coolant flow through the two water jackets in a parallel configuration (i.e., only the inlet and outlet of both the cooling jackets are fluidly coupled).
However, the inventors herein have recognized various shortcomings of the above approaches. The series, or parallel, coolant flow paths may increase the thermal variability within the cylinder head, which may increase the thermal stress on the cylinder head and in some cases cause the cylinder head to warp while the engine is cooling down. Moreover, the two-piece water jacket design disclosed in U.S. Pat. No. 7,367,294 may have a decreased structural integrity due to the design (e.g., layout, shape, etc.) of the coolant passages in the cylinder head. Furthermore, excess gas may build up in the cooling system disclosed in U.S. Pat. No. 7,367,294 degrading cooling operation.
As such, various example systems and approaches are described herein. In one example, a cylinder head for an engine is provided. The cylinder head may include an upper cooling jacket including at least a first inlet and a first outlet and a lower cooling jacket including at least a second inlet and a second outlet. The cylinder head may further include a first set of crossover coolant passages including one or more crossover coolant passages fluidly coupled to the upper cooling jacket and the lower cooling jacket and adjacent to one or more combustion chambers. In this way, it is possible to generate a mixed flow pattern within the cylinder head that is conducive to reducing thermal variability and increasing cooling within the cylinder head and surrounding components while retaining a desired amount of structural integrity.
Vapor may develop in the cooling jackets due to the elevated temperatures in the cooling jackets during engine operation. When vapor is present in the cooling jackets the heat transfer rate from the cylinder head to the coolant may be decreased due to the decreased heat capacity of the vapor when compared to the liquid coolant, thereby degrading cooling operation. Therefore in some examples the cylinder head may include a de-gas port configured to remove gas from the upper cooling jacket, the de-gas port may be positioned in an area adjoining an upper surface of the upper cooling jacket. In this way, gases may be removed from the upper cooling jacket increasing the amount of heat that may be transferred to the coolant from the cooling jackets, thereby improving cooling operation.
In another example a method for operation of a cooling system in an internal combustion engine is provided. The method including flowing coolant into an inlet of an upper cooling jacket from a coolant passage in a cylinder block and flowing coolant into an inlet of a lower cooling jacket from the coolant passage in the cylinder block. The method further includes flowing coolant between the upper and lower cooling jackets via a crossover coolant passage fluidly coupling the upper and lower cooling jackets, the crossover coolant passages positioned downstream of the inlet of the upper and lower cooling jacket and upstream of the outlets of the upper and lower cooling jackets. In this way, it is possible to generate a mixed coolant flow pattern within the cylinder head, thereby decreasing thermal variability within the cylinder head.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.